1. Field of the Invention
The present invention relates to a terminal-modified imide oligomer composition comprising, in a specific ratio, (a) a specific terminal-modified imide oligomer (A) produced by reacting a biphenyltetracarboxylic acid compound with a diamine compound and a monoamine compound having a terminal carbon-carbon triple bond and having an imide bond in the molecular unit thereof, and (b) a low molecular weight unsaturated imide compound (B) obtained by a binary reaction of a substituent-containing nadic anhydride with a monoamine compound containing a terminal carbon-carbon triple bond and having an imide bond in the molecular unit thereof.
The terminal-modified imide oligomer composition of the present invention allows a reduction in the time required for thermal curing during the molding of a composite material, for example, and at the same time, permits an easy production of a prepreg having a used organic solvent substantially extracted therefrom, and can be advantageously used, as a matrix resin in the production of composite materials, as a resin for other molding compounds, and as a hot-melt type adhesive.
Particularly, a laminated composite material produced by thermally curing stacked layers of a fiber-reinforced imide oligomer matrix prepreg using, as a matrix resin thereof, the terminal-modified imide oligomer composition of the present invention, has a high mechanical strength, elastic modulus, and heat resistance, and therefore, can be used extensively in aircraft, machines and vessels for the space industry, printed-wiring boards, and machines and vessels in the electronics field, for example.
2 Description of the Related Art
The polyimide resin has long been used as a matrix resin for shaped articles and fiber-reinforced composite materials, due to its outstanding heat resistance.
Recently, unsaturated terminal group-containing addition type polyimide resins obtained by the reaction of (a) an aromatic tetracarboxylic dianhydride such as pyromellitic dianhydride or benzophenonetetracarboxylic dianhydride with (b) an aromatic diamine and (c) an unsaturated type reactive compound, have been proposed as resins for preimpregnation (see, for example, Japanese Unexamined Patent Publication (Kokai) Nos. 59-167,569, 60-250,030, and 60-260,624). Most of the known polyimide resins of this class, however, have posed numerous problems due to a low solubility thereof in organic solvents, difficulties involved in impregnating same with reinforcing fibers, and the high melting points thereof.
Recently, the present inventors filed an application for inventions related to biphenyltetracarboxylic acid type terminal-modified imide oligomers having a satisfactory solubility (see, for example, Japanese Unexamined Patent Publication (Kokai) No. 1-139,632, Japanese Patent Application No. 63-73,194). When used as matrix resins for preimpregnation, however, the terminal-modified imide oligomers of these inventions are not fully satisfactory because of problems such as an unduly long gelling time, the likelihood of a persistence of an uncross-linked terminal group even after thermal curing, and a low strength of the cured product.
The present inventors, as a solution to the problems mentioned above, then proposed an imide oligomer composition which combines a high molecular weight unsaturated imide oligomer and a low molecular weight unsaturated imide compound having a terminal carbon-carbon triple bond, and filed this invention as Japanese Patent Application No. 63-213,732 (see EP-A-357367).
The above-mentioned composition requires the incorporation therein of an organic solvent, because the components thereof are in a solid state at normal room temperature, and therefore, when used as a matrix resin for preimpregnation, voids are apt to appear during the thermal curing of the prepreg, and a disadvantage arises in that a laminate composite material obtained by thermally curing stacked layers of the prepreg exhibits inferior physical constants. Further, the above-mentioned known compositions are such that, when the prepregs formed of the compositions are stored, the stability thereof is low because the solvents incorporated therein are vaporized and diffused in the air.